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Lightweight foam made of poly(ether‐b‐amide) (PEBA) elastomer has been widely used in sport shoes due to its superior rebounding and supporting properties. Novel PEBA with polyamide 1012 as hard segments and poly(tetramethylene oxide) (PTMO) as soft segments was foamed by supercritical CO2. The influence of foaming process parameters, that is saturation temperature, pressure on the morphology of cellular structure was systematically studied by scanning electron microscopy (SEM) and wide‐angle x‐ray diffraction (WAXD). By controlling the viscoelastic behavior of PEBA at certain temperatures and pressures, foams with low density and energy loss coefficient can be fabricated. The cell density of 4.5 × 109 cells/cm3 and expansion ratio of 16.0 of the foams can be obtained respectively. Cyclic compression performance of foams was systematically studied. For the foams with the highest expansion ratio, the energy loss coefficient of 11.9% in the first cycle and 3.5% after equilibrium were observed, which were less than those of former reported PEBA foams. The relationship between the Young's modulus and expansion ratio is in line with the Gibson–Ashby relationship. [ABSTRACT FROM AUTHOR]

This work investigated the effect of silane modification of halloysite nanotubes (HNTs) on the mechanical properties of epoxy/HNTs nanocomposites. Three kinds of silane coupling agents, including 3-(2-aminoethyl)-aminopropyltrimethoxysilane (AEAPS), (3-glycidyloxypropyl)-trimethoxysilane (GPTMS), and octyltriethoxysilane (OTES), were employed. It was shown that the modified HNTs exhibited a better dispersion in the epoxy matrix compared with pristine one. Because of strong interfacial interaction between AEAPS modified HNTs and the epoxy matrix, the nanocomposites exhibited the highest glass transition temperature and modulus among all the samples. On the other hand, AEAPS and GPTMS modified HNTs/epoxy nanocomposites showed enhanced tensile strength and toughness. The toughing mechanisms were identified by the SEM micrographs of the fracture surfaces of the different kinds of samples. In this study, simultaneous enhancement of strength, toughness, and thermal stability of epoxy by the modified HNTs provides a novel approach to produce high-performance thermosets. [ABSTRACT FROM AUTHOR]

The effect of the final melting temperature (Tf) on the crystallization of poly(L-lactide) (PLLA)/poly(D-lactide) (PDLA) was studied via a combination of differential scanning calorimetry, wide-angle X-ray scattering, polarized optical microscopy, and Fourier transform infrared (FTIR) spectroscopy. We observed that a residual stereocomplex (SC) crystal induced the formation of SC crystals during cooling from a Tf (230°C) just above the melting peak of the SC crystals. On cooling from a Tf (240°C) just above the endset temperature of SC crystal melting [Tm(S)(E)], the possible order structure and the strong interchain interaction promoted the preferential crystallization of SC crystals; this enhanced the formation of a crystals. During cooling from a Tf (≥250°C) far above Tm(S)(E), the crystallization peaks of a and SC crystals converged. The FTIR results indicated that the residual SC crystals, possible ordered structure, and interchain interactions in the melt might have been the key factors for the different crystallization of PLLA/PDLA. [ABSTRACT FROM AUTHOR]

ABSTRACT Propylene-based propylene-ethylene random copolymer (PPR) has been widely used in the production of hot-water pipes. To further improve its toughness and thermal resistance, β-nucleating agents (β-NAs) are frequently incorporated. In this study, PPR containing 5.6 mol % ethylene units was modified by two kinds of β-NAs, that is, calcium pimelate and N,N′-dicyclohexylterephthalamide. The notched Izod impact strength of PPR increased with the addition of the β-NAs. Drastically different toughening effects were found between the two β-NAs. The structure of PPR with and without a β-NA was investigated by calorimetry, X-ray diffraction, and thermomechanical analysis. The results indicated that the relative fraction of β crystals ( kβ) in the injection-molded specimens was determined by the type and content of β-NA. The relationship between kβ and the impact toughness was summarized. A critical value for kβ (0.68) was identified for the brittle-ductile transition of PPR. PPR with β-NA having a kβ greater than 0.68 displayed a higher impact strength than the other mixtures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42930. [ABSTRACT FROM AUTHOR]

ABSTRACT In the present work, the fracture behavior of transcrystallization (TC) of poly( l-lactic acid) (PLLA) in thin film and the dependence of mechanical properties on the morphology of TC have been studied. The nucleation density of TC was merely determined by the annealing temperatures of the fibers which used for inducing nucleation, and the crystallization temperature and time of the samples were completely identical. By using in situ polarized optical microscopy, the fracture process of TCs was characterized. For the TC with high nucleating density (TC-H), lots of cracks were generated from the TC bulk during fracture. But only few cracks were observed on the TC with low nucleation density (TC-L), and the final fracture of TC-L always occurred in the junctions of crystal segments. Compared to the samples which do not contain TC, the fracture strength was enhanced by 8.1% because of the presence of TC-H. On the contrary, the presence of TC-L can reduce the fracture strength of the samples. The fracture surfaces of TC were characterized by scanning electron microscope. It was observed that the fracture surface of TC-H exhibited obvious fibrillation and cavitation, but the fracture surface of TC-L was smooth and featureless. The possible fracture mechanism for two TCs was discussed in view of their intrinsic crystal organizations. © 2014 The Authors Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41273. [ABSTRACT FROM AUTHOR]

To improve the heat resistance of thermoplastic polyurethane (TPU), in the melt blending process polyamide 1212 (PA1212) and trace amount of 4, 4′-diphenylmethane diisocyanate (MDI) were used as modifier and reactive solubilizer, respectively. Compared with pure TPU, the combinatorial addition of PA1212 and MDI resulted in remarkable improvement of mechanical, thermal, environmental, and aging properties of the TPU matrix. The reactive MDI contributes to the better interfacial adhesion between TPU and PA1212, and the dispersed PA1212 particles act as fillers as well as crosslinking points in the TPU/PA1212/MDI ternary blend. It was revealed that the synergetic effect of PA1212 and MDI is responsible for the enhanced performance of modified TPU. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

This study examines the miscibility and mechanical properties of isotactic polypropylene (iPP) and olefin block copolymer (OBC) blends (70/30 wt %). The blends exhibit phase-separated morphology. The OBC domain size decreases with increasing the 1-octene content in the soft segment. The crystallization, melting behavior, and the long spacing of the iPP component in the blends are nearly the same as those of neat iPP, while the T g of the iPP component shifts slightly to lower temperature. 'Blocky' OBC is immiscible with iPP, while the soft segment rich polymers in OBC could be partially miscible with iPP. The impact strength of the blends is greatly increased with increasing the 1-octene content in the OBC soft segment. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

In this report, polyamides were solution blended in the formic acid with poly(vinyl pyrrolidone)(PVP), an amorphous polar polyamide. The thermal behaviors and morphological change in the blends of Nylon 6 (PA6) and PVP were investigated in details via WAXD, DSC, FT-IR and POM methods. The equilibrium melting temperatures for PA6 in the blends were estimated based on the linear and nonlinear Hoffman-Weeks (LHW and NLHW) extrapolative methods. With increasing the mass ratio of PVP to PA6, T m (melting temperature) and T c (crystallization temperature) of PA6 in blends both decreased as well as that of the spherulite size of PA6. The interaction mode between PVP and PA6 was investigated by FT-IR spectroscopy, and the spectral changes indicated that the carbonyl groups of PVP had formed hydrogen bonding with the NH groups of PA6 molecules in the molten state, which resulted in the variation of the morphology and thermal behaviors. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

The article explores the in situ compatibilization of polypropylene (PP) and polystyrene (PS). This was carried out through combinative application of tetraethyl thiuram disulfide (TETD) as degradation inhibitor and di-tert-butyl peroxide as degradation initiator in the process of reactive extrusion. It was shown that peroxide-induced degradation of PP can be effectively depressed by adding TETD, which may promote the development of PP-g-PS copolymer during melt processing.

In situ polymerization was proved to be an effective method to prepare composites with combined properties of two intrinsic different components. In this study, poly(decamethylene dodecanoamide) (polyamide 1012, PA1012) powders with controlled morphologies and crystal forms were obtained by antisolvent precipitation, whose morphology and crystal forms were strongly dependent on the types and temperatures of antisolvents. PA1012/polyaniline (PA1012/PANI) composites with different morphologies were manufactured through in situ polymerization. Fourier transform infrared spectroscopy results revealed a strong interaction between PA1012 and PANI components. PANI components were in situ polymerized from aniline monomers on the surface of PA1012 powders, forming a composite aggregates in solution. The conductivity of different PA1012/PANI composite powders was about 10−5–10−3 S/cm, which could successfully meet the requirement of antistatic coating. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47041. [ABSTRACT FROM AUTHOR]